Technical Field
Certain embodiments of the present invention relate to cryocoolers and cryocooler rotary valve mechanisms.
Description of Related Art
A cryocooler represented by a Gifford-McMahon (GM) cryocooler includes an expander and a compressor of a working gas (also referred to as refrigerant gas). In most cases, the expander includes a displacer that is axially reciprocated by a driving means, and a regenerator that is built into the displacer. The displacer is accommodated in a cylinder that guides the reciprocation. A variable volume formed between the cylinder and the displacer, and generated by the relative movement of the displacer with respect to the cylinder is used as an expansion chamber for the working gas. The expander can give rise to coldness by appropriately synchronizing volume and pressure changes of the expansion chamber.
Accordingly, the cryocooler includes a valve component for controlling the pressure of the expansion chamber. The valve component is configured so as to alternately switch between supply of high-pressure working gas from the compressor to the expander, and recovery of low-pressure working gas from the expander to the compressor. In general, a rotary valve mechanism is used as the valve component. Such valve components are also included in other cryocoolers such as pulse-tube cryocoolers.